Another new blogger, another new tropical storm!

Hi Everyone, I am also new face to this blog! My name is Philippe Papin and like Larry, I am a second year graduate student at the Department of Atmospheric and Environmental Sciences at the University at Albany, SUNY. Unlike Larry, however, I am not a native to the region, as I was born and raised in the Carolinas, where I lived primarily before moving to Albany last year to start graduate school. I graduated with a degree in Atmospheric Science at the University of North Carolina Asheville, making me a Bulldog (NOT a Tar-heel!). My research focuses on tropical meteorology, in particular the genesis of tropical cyclones (like Tropical Storms and Hurricanes) and monsoon gyres (much larger low pressure systems that occur in the tropics). In addition to my research, I am an avid follower of tropical weather and I have the hurricane tracking charts to prove it! I also enjoy discussing a variety of other atmospheric phenomena. With that said, it looks like things might be getting busy in the near future.

Taking a quick look out in the tropics, there are two areas currently worth noting. Tropical Storm Isaac recently developed this afternoon, and there is another tropical disturbance (labeled Invest 96L) that has the National Hurricane Center’s attention. For the interest of time, I’ll just talk a little bit about Isaac today, which could become quite the troublemaker over the next week.

Tropical Storm Isaac

Visible / Infrared Animation of Tropical Storm Isaac

Isaac is only a weak tropical storm right now (40 mph), but the forecast is for intensification as the storm rolls westward into the Caribbean Sea. On satellite imagery (above), you can see that there was a large blow up of deeper convection over the circulation center, which was evident in the first few frames of the loop. Whether or not this is a harbinger for intensification of the system remains to be seen. Another set of tools that tropical meteorologists like to use when investigating tropical cyclones is the plethora of computer models that predict the future atmospheric pattern. However, not all computer models are created equal. Some models are merely statistical in nature, in that they project a forecast track and intensity based off other cyclones in the past that crossed that same path. However, many models are dynamical, in that they are able to take the initial physical conditions of the atmosphere and use mathematical equations to forecast a possible solution. Finally, some models are a combination of the two methods mentioned above. Taking a look at a track map of all these different models shows that there is a general consensus in the guidance, taking Isaac generally to the west-northwest through the Greater Antilles. This track consensus seems very much in agreement with the National Hurricane Center’s forecast over the next five days. This track also hints at a possible threat to the United States down the road. Of course, the speculation continues beyond this time frame, and thats where meteorologists often turn to an additional tool. Ensemble prediction.

For this long range forecast, lets look at two different sets of ensemble guidance, the Global Forecast System (GFS) Ensembles and the European Centre for Medium Range Weather Forecasting (ECMWF) Ensembles. Ensembles are a suite of computer models based on a particular dynamical model. In this case the models are the GFS and the ECMWF. Each model is run dozens of times, each iteration with slightly different initial conditions run forward in time. These differences at first are very small, but soon magnify with time as small changes in the model input lead to large changes in the output atmospheric conditions. This divergence of solutions with time in dynamical systems is popularly known as chaos theory. Getting back to the meteorology of it all, we can plot a mean value of all of these various solutions on a map, as seen above. Here we see that the ECMWF ensembles projecting a stronger mid-level ridge to the north of Isaac in comparison to the GFS ensembles which open up a weakness, or gap, in the ridging. Due to this weaker mid-level ridge, Isaac is able to move further north in the GFS ensembles. Since this is a mean value, outlier solutions, or solutions that are outside of the model consensus, are less likely. The main take home message from this model guidance is that most of the ensemble members have Isaac threatening the United States beyond the traditional forecasting range. With that said, this is a day seven forecast, which has a large degree of uncertainty. However, there is a growing consensus that the US may have to face a significant storm in the week to come. Interests in the Gulf of Mexico and the southeastern US coastline should keep a close eye on the evolving track of Isaac.

Thats all I have for today. If you have any questions about Isaac, or even any of the other topics described above, feel free to leave a comment below. I look forward to interacting with you all in the Times Union blogging community!

3 Responses

Welcome Mr. Papin. I like the use of the color coded models to illustrate your point as I clearly see the weakness you are referring to. I know we are really far out but Im hoping this doesnt impact Labor Day weekend in our neck of the woods. I cant rid my thoughts of another “Irene”. Needless to say, anyone on the southeast coast needs to keep areast before we will know where this heads later on.

You hit the nail on the head. At this point, the best thing residents along the coastline can do is watch the storm and keep up to date with the latest information. At this point, there are still a lot of unknowns to work out, namely how much of the storm will survive the impact of the high terrain across Cuba and Hispaniola. Its still difficult to gauge if the system will recover substantially before a potential landfall in the United States.